North American van semi-trailer is designed and manufactured according to AAR (Association of American Railroads) M931 standard, wherein the North American van semi-trailer is an enclosed van body, one end of the bottom surface of which is provided with two or three pairs of wheels, the other end of the bottom surface of which is provided a leg for supporting the van body. When transporting the van semi-trailer, the end provided with the leg is connected to a specific tractor and the leg is retracted upward, thereby the van semi-trailer can be transported by means of the driving power of the tractor.
Since the van semi-trailer is directly connected to the tractor during the transportation of the van semi-trailer, it is not necessary to stack a plurality of the van bodies and move them through other modes, thereby such a van semi-trailer has a quite simple structure. As shown in FIGS. 2-5, the van body typically only comprises a base frame 11 in a rectangular skeleton form, four upstanding posts 12 extending upwards from the four corners of the base frame 11, two top longitudinal beams 14 connected with the four upstanding posts 12 along the length direction of the van body at the top of the van body, a plurality of top transverse beams 13 connected between the two longitudinal beams 14, and a front wall panel 15, a door panel 16, side panels 17 and a top panel for defining the enclosed van body from the front, rear, side and top directions, respectively. Other parts below the base frame 11, such as wheels 19, a leg 18, a mud baffle 10, and so on, belong to detachable parts.
The North American van semi-trailer is mainly and widely applied in the inland region of North America. However, in the field of van semi-trailer, it is an important and difficult problem to transport van semi-trailers in batches from a manufacture site to a use site, for example from other regions out of the North America to inland region of the North America.
The first considered factor with respect to above problem is about the cost of transportation of the van semi-trailers. At present, it is the lowest cost and most convenient way to transport the semi-trailers by ship. Although other alternative modes may be available, these alternative modes involve very high cost of transportation, thereby it is not advantageous for these alternative modes in competitive with the manufacture of the van semi-trailer in the use site (i.e. inland region of the North America). Therefore, when the van semi-trailers are transported by means of ships and docks in current movement or storage modes, it still is bottleneck problem how to transport van semi-trailers from a manufacturing site to a use site.
At present, container transportation ships and corresponding facilities in dock, such as a tower crane, are manufactured and equipped according to ISO1496 for the standard container. When containers arrive at a harbor, the containers will be lifted and moved by the tower crane by connecting the top of each container, so as to put each container onto a ship and stack to a certain height according to the requirement of load-distribution of ship. Therefore, in order to transport the containers by ship, the requirements of the lifting devices and a certain stacking property of the containers shall be met. As shown in FIG. 1, an ultra-long North American container 1′ has two parallel stack frames 11′ which are spaced at prescribed interval along the length direction of the container and receive the load from another stacked container; top corner fittings 12′ and bottom corner fittings 13′ in conformity with the ISO standard are provided at the top portion and the bottom portion of the stack frames 11′, respectively; four lift holes are formed in the four top corner fittings 12′ respectively, four stack holes are formed in the four bottom corner fittings 13′ respectively. According to the standard size of the tower crane, the distance between two lift holes along the length direction of the container is 11,989 mm or 5,855 mm, and the distance between two lift holes along the width direction of the container is 2,260 mm.
However, as for the current van semi-trailer, the structure of the current van semi-trailer has not a necessary design on a stack frame, stack holes and lift holes, and thereby this structure can not meet the requirements of lifting and fixing in dock and on ship.